This invention relates to a valve device and more particularly, but not exclusively, to an apparatus for coating an elongate member with a selected one of a plurality of different resins, which apparatus incorporates a valve device.
Optical fibres are coated with resin immediately after drawing from a preform to protect them from damage. Typically, such fibres are provided with two coatings, the first being a low modulus coating to buffer the fibre from lateral pressure and the second being a harder and more robust coating to protect the first coating, and hence the fibre, from mechanical damage. The coating is also advantageously used for identification purposes by being coloured. Colouring of the coating is conventionally achieved by `inking` it in a separate operation after its application, but this is disadvantageous as it adds an additional step to the manufacturing process.
The use of a coloured resin for the visible coating (i.e. the second coating in the two coating arrangement discussed above) would eliminate the need for the `inking` step but presents its own problems. In particular, unless it were possible to dedicate separate fibre drawing lines to each colour, there is a need to clean the resin applicator each time it was required to change the colour of the visible coating. This requires not only labour but also causes a loss in production due to down-time and furthermore disruption of the applicator set-up. One solution to these problems is to provide the drawing line with a plurality of resin applicators each for applying a different coloured resin. However, this solution has the disadvantage of requiring a longer drawing line in order to accommodate the extra applicators and also the setting up of the extra applicators.